1. Field of the Invention
The Present invention is related to semiconductor chip manufacture and more particularly to wafer carriers for Chemical Mechanical Polishing.
2. Background Description
One typical use of Chemical Mechanical Polishing (CMP) in semiconductor manufacturing is for removing superficial topographical irregularities in a surface layer of a semiconductor wafer. However, the edge regions of the wafers polish faster than the center regions causing non-uniformity in the finished thickness of the polished film.
Uneven polishing occurs in CMP processes because the wafer being polished compresses the polishing pad, causing higher pressure at the edges of the wafer. That higher pressure also prevents even slurry distribution. Less slurry works towards the center of the wafer than is available at the edges. Compression rings for pre-compressing the pad may solve the edge pressure problem, but do not improve slurry distribution.